Radio signaling system



1,632,369 J 14,1927 A. CROSSLEY RADIO SIGNALING SYSTEM Filed Oct. 12. 1925 Ay wd Crossfpy.

Jun -F 1927- 1 "[UNITE STATES PATENT OFFICE.

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application flleQ October 12, 1925."Seria1 No. 62,199.

.--'My invention relates broadly to electron tube signal transmission systems and. more particularly to means for keying or controling the output power of an electrontube transmitting apparatus. 7 I

" One of the objects of my invention, is to control the output ower of an electron tube oscillator 01'- ampli' 'er by means of a change in the amount of negative gridvoltage from a high value or minimum, or zero power output, to a lower or optimum value which permits maximum output from an associated transmitting apparatus.

Another object of my invention is to provide means for maintaining a constant value of negative grid voltage in an electron tube transmitter with no appreciable increase in power from this source of negative grid voltage. g

Still another object of the invention is the provision of a method for increasing atwill the efficiency of the electron tube transmitter or amplifier without any appreciable effect on the plate or negative grid source. of power.

Heretofore in the art resort was made to the use of the voltage drop over a resistance placed in series with the plate power source of an electron tube circuit as a means for so obtaining negative grid voltage but this method proved to have certain limitations such that the power output of the transmitter or, amplifier was automatically kept at a certain value irrespective of the change of plate voltage. Another method of grid volt power drawn from the negative grid voltage source and at the. same time itrequired special heavy current carrying resistors to handle the increase in current. The short circuiting was also attended by bad sparking at the relay contacts controlling the formation of signals. Obviously, these two prior methods were not suited for best efliciency' and flexibility of operation, and I have devised the method described herein for overcontrolled electron tube radio 'lator-power amplifier type of electron tube power for thecrystal controlled oscillator.

coming the disadvantages inherent in systems of the prior art.

My invention will be more clearly understood from the specification hereinafter following by reference to the accompanying drawings, in which:

Figure l'is a diagrammatic view showing an embodiment of my invention in a crystal v v transmitter; and big. 2 shows a modified circuit diagram for a self oscillation electron tube transmission c rcuit embodying the principle of my invention. i

In Fig. 1 there is shown a crystal osciltransmitter, the crystal oscillator radio frequency power output being continuous while the power amplifier output is controlled by a keying or control system. In the drawin reieren'ce character 1 shows the piezo electric crystal with its two contact plates 1 and l 2 1S the grid radio frequency choke with a negative battery source 3 connected therewith as a means for obtainingnnaximum eificiency of control from the piezo electric crystal on the grid electrode of electron tube 4. A filament heating battery 5 and a plate supply battery 8 furnishes the required- Plate radio frequency choke 6, by-pass condensers 6 and 7 together with the oscillation circuit 9 complete the assembly of the crystal controlled oscillator system. 1 SufiEicient-ra'dio frequency crystal voltage 1s tapped from the inductance coil of cir cuit 9 to provide proper exciting voltage for the :grid. of electrontube 12. i To prevent short :circuiting of the negative voltage souroeastoppi'ng condenser 10 is provided. The "radio frequency choke 11 permits the negative voltage to be placed on the grid electrode 12 and at the same time preventshort circuiting of radioit'requency excitation voltage through negative supply source. The'battery 14 and the otentiometer resistance 1'5 provide'means or obtaining desired negative voltages for blocking the grid or operating the grid at its most efiicient point on the grid voltage plate current characteristic curve. The blocking voltage flows through the high resistance 17 to the grid 12 when the key 19 of the relay circuit 18 and 16 is open, while with the key down, the blocking voltage is taken off by virtue of the fact that the relay contacts 30 now connect no the grid circuit to the midtap 31 on the potentiometer which lowers the voltage to the voltage corresponding to that at the midtap 31. v I

The fact that a very high resistance is employed at 17 permits a very slight increase in the loadon battery 14, because this resistance when placed in parallel with a portion of the potentiometer resistance does not materially decrease the value of resistance by virtue of the parallel path through the relay contacts 30. In the drawing thev potentiometer resistance 15 is shown with the tap 31 substantially at the mid point on the resistance, but in practice this point is at any point along the resistance where best negative operating voltage is obtained. Should itvbe required to provide an additional tap or contact on this resistance to control another grid circuit this can be done by providing another relay system and a second contactor thereby using the same voltage source for two or more transmitters.

This latter condition can only be'accomplished with my system, because the act of eying does not appreciably aflect the load on the negative battery source. The value of resistance 15 should be such that the rect1- fied current will have little effect on the total voltage drop over this resistance when the key is down while the resistance 17 should be at least 50 times the value of the portion of resistance 15 which is parallel with it through the relay contacts 30.

The fact that a high resistance is shunted across the portion of resistance 15 through the relay contacts allows only a very small amount of sparking at the relay con-.

tacts 30 which is very desirable.

I have shown the electron tube 12 with its output circuit connected to antenna ground system 34. with tuning inductance 32 arranged therein. The output circuit of tube 12 includes coil 39 and high potential battery shunted by by-pass condenser 41. The plate circuit of tube 12 is coupled through condenser 38 with the tuning inductance 32.

In Fig. 2 there is shown a tuned plate type of electron tube oscillator where, the plate and grid coils 32 and 33 are connected with the tube circuits. The plate coil 32 isconnected between antenna 34 and ground 35 while the grid coil 33 is connected to the grid through condenser 36.

The control of oscillations is accomphshed through grid choke, 2, by a similar negative voltage system which was previously de scribed in connection with Fig. 1.

The invention described herein has been found to be very practical in construction and operation. The operating characteristics of the electron tube system may be changed at telegraphic speeds in the producthe tube system the tube functions sufficiently for the transmission of signals or the tube is completely blocked with respect to the signaling energy. Proper values of resistances 17 and 15 are selected for the efficient operation of the tube system.

While, I have described my invention in certain preferred embodiments, I desire that it-be understood that modifications may be made and that no limitations upon the; invention are intended other than are imposed by the scope of the appended claims.

, What I claim-and desire to secure by Let- 15ers Patent of the United States is as folows:

1. In a signaling system the combination of an electron tube having grid, filament and plate electrodes, in ut and output circuits.

interconnecting sai electrodes, a source of negative potential arranged to be normally connected with said grid electrode, a resistance interposed between said source and said grid electrode, a potentiometer shunted across said source, an independent connection between a point along said potentiometer and said grid electrode, a relay system, relay contacts actuated by said relay system and interposed in said independent connection on opposite sides of said resistance, and a keying circuit for controlling said relay system whereby said grid electrode may be normally connected with said source of negative potential, and said connection shifted to said point along said potentiometer for changing the value of the negative potential on said grid electrode in accordance with the operation of said keyingcircuit.

nal transmission system, the combination of an electron tube having. grid, filament and plate electrodes, input and output circuits interconnecting said electrodes, a source of negative potential having one end thereof connected with said filament electrode and the opposite end thereof connected with said grid electrode, a resistance interposed in series with said last mentionedconnection and having a value for normally establishing a high grid blocking voltage, a potentiometer connected in shunt with said source, a relay system including contacts and an operatin solenoid, a keying circuit connected with sai operating solenoid, connections between said contacts and points along said resistance and said potentiometer whereby a portion of said potentiometer-maybe connected in parallel with said r'esistanceupon operation of said circuit for changing the value of negative potentialon said grid electrode, and

shifting the operating characteristics of'said electron tube in accordance with signals.

tion of si als. By changing the amount of nal transmissionsystem the combination of negative i otential .in the grid electrode of an electron tube having grid, filament and meaaee 19 mg a value proportioned to permit the establishment of a high grid blocking voltage, end a relay system connected with said independent resistance and with a selected point on said first mentioned resistance for reducing the value of said grid blocking voltage in accordance with signals without materially increasing the power obtained from said source of negative potential.

ALFRED CROSSLEY. 

